In U.S. Pat. No. 5,070,642 there are shown and described ground locks to prevent root-control elements from being lifted up in the ground by the tree roots that pass beneath them. It is significant that all of the root-control elements shown and described in that patent are panels, which panels are in some instances used in flat condition and in some instances are combined with other panels to form circular (closed-loop) planters. The planters are used around the root balls of newly planted trees to direct the tree roots downwardly to such depths that nearby sidewalks and other static structures are not cracked or lifted by the roots.
There exist planters that are integral--do not need to be assembled from panels. Because there is no need for any assembly, much labor is saved. However, in no instance known to applicant has any such integral planter incorporated a ground lock. Furthermore, such integral planters were quite thick-walled, heavy, expensive, etc. In addition, such integral planters generally require considerable space while being shipped and stored in stacked condition.
It is easy to injection mold a ground-lock ledge as an integral part of a panel, the ledge being positioned to be engaged by tree roots and thus held down, which in turn holds down the panel. (This is not to imply that conceiving the concept of ground locks--as distinguished from manufacturing them after conception has occurred--was at all easy.) A panel can be injection molded flat, with both sides thereof readily accessible to the mold elements, which means there is no problem in molding ground-lock ledges integrally with the rest of a panel. However, an integral planter is frustoconical or otherwise downwardly divergent, and nobody has previously conceived how ground locks may be incorporated therein.